I didn't say the first thing. And the first thing is a procedure, as described in the second sentence.
If the procedure permits the GM to just act as they fancy, though, then I think we've moved out sandbox territory and into a "living novel" approach.
So if the GM makes a call without procedural restraints, it can't be a sandbox. According to you and, from the couple dozen articles and links I read not to mention every description of sandbox I've heard from anyone else, is something only you require.
Here, the relevant constraint seems to be "what I know about the NPC". You haven't said where that comes from.
In D&D I'm responsible for all of the fiction other than the PCs.
In the classic D&D sandbox, if the NPC is a newly-introduced character (eg via a random encounter), then the first thing that the GM will know about the NPC is whatever it says about that sort of person in the Monster Manual; and the second thing will be the outcome of the reaction dice.
That's not anything I've ever heard or seen done. The vast majority of NPCs I've ever encountered in D&D over decades were created by the DM not random table generation.
I didn't say anything about your preference.
I responded to this thing that you posted: "As long as the GM is not forcing a direction I don't care if the location, obstacles or opportunities are predetermined, procedurally determined, made up on the spot. All that matters is the entertainment value". Now it turns out that your preference includes other things, like taking into consideration the world that has been envisioned.
I still can't tell whether or not you're advocating for "living novel", because you haven't said much about when and how the GM's envisioning of the world takes place. In my view, what characterises sandbox-y play is that the player can make choices about what is at stake for their PCs - information and context aren't always perfectly known, but aren't blind either. The GM taking into consideration the world that has been envisioned (by them) is consistent with both informed and blind choice on the player side.
Sandboxes involve the players making decisions and declarations for their characters. Unless you're changing the default approach in D&D that means they make decisions based on what their characters know and their actions are limited to what their characters can do. As I would assume you well know. How those declarations are handled depend on the game and preference. I've never heard of the term "living novel".